I have in in my head that most of the “in the truck” main seal replacements I’ve read about here…have involved the rope seal.
Can the neoprene seal be installed “in the truck” as well?
It might be worth a try, but would be the opposite of pulling the top half through with a sneaky pete tool. The neoprene is two stiff semi-circle pieces. You'd have to push the top half through, starting underneath the crank and rotating it up and over. Would likely require alot of lube...and that's the very condition that might make the whole thing spin after installation (not good!).
Maybe there'd be a way to pull it over with a sneaky pete type rig, I dunno. There's no good way to do it in the truck, and seems there's only one good way out of the truck, and that involves machining cap and block for a one piece seal.
Thinking further, (and that's all this is...the imagination of a rookie noob engine builder, so be careful following my advice!!) if you could lower the crank maybe 1/4 or 3/8 inch you could set the top neoprene half on top of the crank exactly in line with the seal groove, then raise crank and seal into the channel just right.
It could be done. Worth a try, IMO.
